9457

• UCREFRP Catalog Number: 9457
• Author: Ptacek, J. A., D. E. Rees and W. J. Miller.
• Title: A Study of the Ecological Processes on the Fryingpan and Roaring Fork Rivers Related to Operation of Ruedi Reservoir.
• USFW Year: 2003.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

Results provided by these metrics indicated that high densities of benthic
macroinvertebrates occur in the Fryingpan River downstream of the reservoir during the
spring and in the Roaring Fork River near Carbondale during the spring and fall (Figure
41). Biomass was generally greater during the spring with the highest values occurring at
RFR-C during spring 2002 (Figure 42). Densities ranged from 10,318 individuals/m2 at
FPR-TC in the fall of 2001 to 62,996 individuals/m2 at FPR-RES during the spring of
2002. Biomass ranged from 1.38 g/m2 at FPR-RES in the fall of 2001 to 16.87 g/m2 at
RFR-C in the spring of 2002. The dissimilarity between these two metrics was apparent
on several occasions. A difference in size and/or species composition is usually
responsible for dissimilarities in trends between density and biomass.
The previously described metrics were used to evaluate benthic macroinvertebrate
communities in terms of structure. Separating invertebrate taxa into functional guilds
based on food acquisition provided a measurement of macroinvertebrate community
function. Aquatic macroinvertebrates were categorized according to feeding strategy to
determine the relative proportion of various groups. The proportion of certain functional
feeding groups in the macroinvertebrate community can provide insight to various types of
stress in river systems (Ward et al. 2002)
An examination of the function of benthic macroinvertebrate communities, in terms of
food acquisition, can also provide insight into the overall health of the ecosystem.
Results of functional feeding group analysis indicated some spatial and temporal changes
(Figure 43). Communities immediately below the dam were consistently dominated by
collector-gatherers, while other functional groups became more apparent downstream.
The shredder and scraper guilds were well represented on each sampling occasion from
FPR-TC downstream to RFR-HB. Collector-filterers and predators generally comprised
a lower proportion of the functional group composition at most sites throughout the study
period.
Draft Final Report, Fryingpan and Roaring Fork Rivers February 12, 2003
Miller Ecological Consultants, Inc. Page 48